The present invention relates to telecommunications systems employing digital switching and is more particularly concerned with the provisions of security arrangements involving cross-office path duplicated connections for use in such systems.
The switching networks used in telecommunication exchanges which handle digital data transmission carrying connections (such as pulse code modulation handling connections) are organised in accordance with so-called time division switching involving both time and space division switching techniques. Security in such switching networks is always a significant problem because of the high traffic carried by the time-shared highways and switching stages constituting the switching network. Schemes have been proposed in the prior art in which "M in N" types of sparing are provided for the various component parts of the switching network. However, such procedures pose severe problems of cabling and timing between main and spare units and add appreciably to the complexity of switch path selection arrangements.
To overcome such problems it has been suggested that the trunking in a digital switching network should be completely duplicated between the exchange receive and transmit transmission interfaces and it is an aim of the present invention to provide arrangements in the exchange transmission interfaces which exploit the provision of the duplicated switching planes to enhance the information handling security of the exchange.